Tumblr launched an updated iOS app on Tuesday that includes a "very important security update" to address an internal flaw.

In a company blog post, the Yahoo-owned microblogging site urged users of its iOS app to "please download this update now" and change their passwords on the site, as well as on other sites where the same password is used.

The security issue, the nature of which was not described in the post, apparently does not affect the Android version as no update for that app was issued.

Yahoo did not immediately respond to a CNET request for more information but did tell TheNextWeb that it only learned of the vulnerability on Tuesday:

Earlier today, Tumblr was notified of a security vulnerability introduced in our iOS app. We immediately released an update that repairs the issue and are notifying affected users. We obviously take these incidents very seriously and deeply regret this error.

The microblogging site, which claims to have more than 300 million monthly unique visitors, was acquired by Yahoo last month for $1.1 billion.